The invention relates to a continuously operating sedimentation filtration installation for cleaning contaminated processing liquids such cooling agents; hydroforming water; drilling, rolling, grinding, and turning emulsions; rinsing water; and the like. The installation is comprised of a sedimentation container with a plurality of plate-shaped filter elements arranged at a slant and extending parallel to one another at a spacing to one another. The filter elements together form a filter body. The installation further comprises a removal device for the deposited sediment, a supply opening into the sedimentation container for introducing contaminated processing liquid, and a clean liquid tank connected to an overflow of the sedimentation container and configured for receiving the filtered processing liquid.
Sedimentation filtration devices are used for cleaning processing liquids which are contaminated during a production or machining process by particles whose relative density is greater than that of the actual processing liquid. These particles settle in a container as a result of the gravity acting on them and form a so-called sediment which must be removed from the sedimentation container by means of suitable devices.
In order to increase the settling speed of the particles and thus the throughput of such a device, plate-shaped filter elements are arranged according to the prior art in the interior of the sedimentation container and are positioned at a slant and spaced from one another by means of spacer elements.
By means of the described arrangement of the filter elements, the deposition path of the individual particles is drastically reduced; in the known devices, it is presently approximately 5 to 15 mm.
As a result of shortening the deposition path, the dirt particles to be removed practically do not disturb one another during deposition so that the cleaning effect and capacity of such devices is increased in comparison to simple settling containers.
The sediment deposited on the filter elements is removed by means of blowpipes arranged underneath the filter body, wherein, in the case of large size installation, the filter elements are brought into a vertical position by suitable adjusting devices for the task of blowing off the sediment.
The thick particle cake then sinks from the filter elements onto the bottom of the settling container from where it is removed by scraper belts or similar removal devices.
In the known devices, the processing liquid to be cleaned is supplied by means of a supply pipeline adjacent to the filter body such that the processing liquid flows mainly laterally into the filter body.
In order to prevent that air bubbles, which would disturb the settling process, are introduced with the processing liquid into the sedimentation container, the supply lines have sufficiently sized venting lines. Since during cleaning of the filter elements by means of compressed air it is advantageous to have a low liquid level, this level can be adjusted by means of pumps.
The cleaned processing liquid passes through an overflow in the sedimentation container into a clean liquid tank from where it can be returned into the corresponding machining or production process.
In addition to removal of dirt particles of higher relative density from the processing liquid, there often occurs a contamination of processing liquid with so-called foreign oil, in particular, in metal processing, wherein the foreign oil has a smaller relative density in comparison to the processing liquid and, as a result of this, will float to the surface of the liquid in the sedimentation container. At the surface, it can be skimmed off by corresponding weirs and removal devices, wherein the overflow from the sedimentation container to the clean liquid tank is arranged closely underneath the upper liquid level.
In the known sedimentation filtration devices of the afore described configuration and function type, the processing liquid to be cleaned is supplied via a pipeline having a comparatively minimal flow cross-section and opening laterally adjacent to or before the filter body. The free space which is formed underneath the filter body is relatively low in the devices of the prior art because it is desired to have a minimal height of the entire installation.
The described filtration devices however have a minimal throughput and are prone to disturbances when an increased dirt loading of the processing liquid is present.